Process for the production of orientated synthetic filaments

ABSTRACT

1. A PROCESS FOR THE PRODUCTION OF ORIENTED CONTINUOUS FILAMENTS OF POLYESTTERS OR POLYAMIDES OF FIBER-FORMING MOLECULAR WEIGHT BY SPINNING THE POLYMER AND ORIENTING THE RESULTING FILAMENT BY STRETCHING IN WHICH THE SPINNING AND STRETCHING ARE CARRIED OUT AS A SINGLE CONTINUOUS PROCESS, WHICH COMPRISES AS A SERIES OF SUCCESSIVE STEPS, ONE FOLLOWING IMMEDIATELY ON ONE ANOTHER IN THE FOLLOWING ORDER: (A) EXTRUDING AS CONTINUOUS FILAMENTS THE MOLTEN POLYMER INTO AN ATMOSPHERE AT SUBSTANTIALLY THE AMBIENT TEMPERATURE; (B) COOLING THE FILAMENTS SO FORMED DIRECTLY TO A TEMPERATURE T1 BETWEEN 55* AND 130*C. WHICH IS (I) ABOVE 55*C., (II) AT LEAST 5*C. ABOVE THE SECOND ORDER TRANSITION TEMPERATURE OF THE POLYMER, AND (III) NOT HIGHER THAN THE MAXIMUM TEMPERATURE AT WHICH STRETCHING FILAMENTS OF THE POLYMER ORIENTS THEM; (C) POSITIVELY FORWARDING THE FILAMENTS WHEN THEY HAVE REACHED THE SAID TEMPERATURE T1 AT A SPEED V1 HIGHER THAN THE EXTTRUSION SPEED, WHEREBY THE FRESHLY EXTRUDED FILAMENTS ARE ATTENUATED WITHOUT BEING SUBSTANTIALLY ORIENTED;   (D) COOLING THE FILAMENTS FURTHER TO A TEMPERATURE T2 BELOW 75*C. WHICH IS ALSO BETWEEN T1 AND THE AMBIENT TEMPERATURE, BY CAUSING THEM TO CONTINUE TO TRAVEL THROUGH AN ATMOSPHERE AT THE AMBIENT TEMPERATURE; AND (E) POSITIVELY FORWARDING THE FILAMENTS WHILE THEY ARE AT THE SAID TEMPERATURE T2 AT A SPEED V2 WHICH IS GREATER THAN V, THE RATIO V2/V1 BEING FROM 3:1 TO 6:1, WHEREBY THE FILAMENTS SO PRODUCED ARE ORIENTED.

Oct. 8, 1974 ca. M. BARBE ETAL 3,840,633

PROCESS FOR THE PRODUCTION OF ORIENTATED SYNTHETIC FILA IEHTS OriginalFiled June 11. 1968 Bum/mks. GERARD [9 /918135 I 25km: OURT'H-kflfCLAUDE LEQMY m WM, M v- MM ATT' ENE Y5 United States Patent 3,840,633Patented Oct. 8, 1974 Int. Cl. 1501f 3/10 US. Cl. 264-210 F 5 ClaimsABSTRACT OF THE DISCLOSURE The invention provides a process for thepreparation of orientated synthetic filaments wherein continuousfilaments extruded from a molten mass of linear synthetic polymer, e.g.polyhexamethylene adipamide or polyethylene terephthalate, are cooled toa temperature above 50 C. and at least 5 C. above the second ordertransition temperature of the polymer, but not above the initialorientation temperature; positively driven at a speed above theextrusion speed; cooled from this to a lower temperature which is stillnot less than ambient temperature and positively driven at a stillhigher speed. The process is easily controllable and enables filamentsof uniform and desirable tensile properties to be obtained.

This is a continuation of Ser. No. 736,229, filed June 11, 1968 and nowabandoned.

This invention relates to orientated synthetic filaments and theirproduction.

In order that filaments based upon linear synthetic polymers andobtainedby melt extrusion may have good mechanical properties, it isnecessary that the polymer in these filaments should have a certaindegree of crystallinity and orientation. This orientation is produced bystretching, at a temperature below the melting point of the polymer,either an already crystalline filament or an amorphous filaments. In thelatter case, the orientation generally produces an incipientcrystallisation.

In the processes at present most widely employed in industry, theextruded filaments are wound after cooling and subjected, in asubsequent phase, to the stretching operation, which is carried out withor without heating, depending upon the polymers and the nature of thefilaments to be obtained. 1

Various single stage extrusion-stretching processes have been described,wherein the stretching may be effected by various means. For example,the extruded and solidified filaments may be taken up at a very highspeed, in such manner that a sufiicient' tension is imparted to thefilaments for bringing about an orientation.

v This tension necessary for the orientation may also be obtained bymeans of the frictional forces imparted to the filaments as they passcontinuously, after extrusion, through a liquid bathof appropriatedensity and at appropriate temperature.

.-While these two types of processes afford various advantages, they'donot make it possible either to control accurately the. extent of stretchimparted to the filament or to obtain filaments having a high degree oforientation.

The simple combination of a conventional device for extruding thefilament with cooling and of a stretching device merely makes itpossible to obtain filaments of comparable quality to the filamentsobtained in two separate stages. Moreover, filaments which must behot-stretched must be. supplied with calories as in the conventionalmethod. Whether this supply of calories be effected by passing thern'ove'r a'he'ated surface or through an atmosphere at appropriatetemperature, it results in a heating of the yarn and of the filamentswhich is not uniform from the centre to the periphery and consequentlyproduces a transverse heterogeneity of the stretched yarn and filaments.

The present invention provides a new process for the production oforientated synthetic filaments, wherein continuous filaments extrudedfrom a molten mass of linear synthetic polymer are: (a) cooled to atemperature of T which is above 50 C.,

and at least 5 C. above the second order transition temperature of thepolymer, but not greater than the.

initial orientation temperature;

(b) positively driven at a speed V higher than the extrusion speed;

(c) brought to a temperature T which is between T and ambienttemperature; and

(d) positively driven at a speed V which is greater than The initialorientation temperature, to which the temperature of the thread mustfall before it undergoes the first positive drive is measured asfollows:

A polymer in the form of a filament is extruded and wound inconventional manner after solidification; at the same time, thetemperature along this filament between the spinneret and the windingpoint is measured by means of a temperature detector for a movingfilament; the curve of this temperature is plotted as a function of thedistance from the spinneret. The filament is then cut at the level ofthe spinneret and there is extracted from this point, a-

length equal to the distance between the spinneret and the windingpoint. After it has been verified that the varia tion of thecross-section of the thread over this length is identical to thatexisting in the course of the spinning between the spinneret and theWinding, the birefringence is measured point-by-point commencing at theend corresponding to the spinneret, and the distance from which ameasurable birefringence appears is noted. By plotting the value of thisdistance on the temperature/distance from the spinneret curve, theinitial orientation temperature T is determined.

The second order transition temperature of the polymer T is measured forthe purpose of the invention on a mois peratures for the variouspolymers concerned being well known.

It is well known that the speed of extrusion is a function of thecross-section of the extrusion orifices, of their number and of the rateof flow of molten polymer. It does 1 not constitute a criticalcharacteristic of the invention and.

may vary within very wide limits.

The cooling of the filaments to a temperature at most equal to theinitial orientation temperature T is influenced by a number of factors,and notably by: the count of the filaments, their speed of travel, thetemperature of the atmosphere through which the filaments pass, and thelength of the zone traversed.

The means by which the cooling of the thread can be most readilycontrolled is the temperature of the atmos phere through which itpasses. The other factors, i.e.1

count, speed of the filaments and length of the zone through which theypass, are generally determined by technological requirements andconsiderations of production.

An atmosphere at ambient temperature may be employed withoutdisadvantage, as also a gas at higher temperature, but the latter is atmost equal to T When the filaments have been cooled to a temperature T,as defined above, they are positively driven at a speed V above theextrusion speed V The upper limit of the ratio V zV is determinedessentially 'by the rheological parameters of the polymer.

The filaments are thereafter cooled to the temperature T Thistemperature T is preferably a few degrees lower than T It is generallymade lower than T notably in the case of condensation polymers.

The length of this second cooling zone and the temperature of theatmosphere obtaining in this zone are the two factors which can be mostreadily varied for operating under the characteristic temperatureconditions of the process according to the invention.

fit is preferable to neutralise the static electricity on the filamentsand this can be done, while cooling them, by passing them through asolution which simultaneously cools them and provides them with acoating of antistatic agent.

After having reached the temperature T the filaments are driven at aspeed V higher than V The ratio V :V is chosen as a function of theextent of stretch which it is desired to impart to the filaments. It isgenerally between 321 and 6:1.

The time for which the filaments are kept in the orientation zone attemperatures above T influences the degree of crystallinity of thefilaments.

-An additional crystallisation may optionally be produced by thermaltreatment of the orientated yarn. This thermal treatment may be carriedout in various ways: after the filaments have reached the temperature Tthey may again be brought to a temperature above T either continuouslyor in the course of a separate operation. The thermal treatment may becarried out under conditions such that the yarn contracts, retains itslength or undergoes re-stretching.

The process according to the invention is applicable notably to:condensation polymers such as polyamides and copolyamides obtained bycondensation of diacids and diamines, e.g. polyhexamethylene adipamide,or aminoacids, e.g. polyundecanamide, or by polymerisation of lactams,e.g. polycapronamide; polyesters such as polyethylene terephthalate andcopolyesters comprising at least 75% of ethylene terephthalate units inthe chain; and to addition polymers such as polypropylene.

For carrying out the process of the invention it is desirable that themeans employed to drive the filaments at the speed V should not suddenlychange the temperature of the filaments at this point.

Preferably, rollers maintained at the same temperature as the filamentsare employed. However, the temperature of the rollers employedinfluences the properties of the filaments, and more particularly thecontraction properties, and it may be desirable to utilise this factorin the preparation of filaments having particular character istics.

The preferred means for driving the filaments at the speed V: are alsorollers which may be either at the temperature T or at a highertemperature, depending on whether or not it is desired to subject thefilaments to a thermal treatment at this point.

In the process of the invention, the dynamometric properties of thethreads which it is desired to obtain can be precisely controlled, andproducts having high regularity of count and a good structuralhomogeneity can be continuously prepared.

The process according to the invention affords the possibility ofstretching very uniformly the various filaments of a multi-filamentproduct, since the distance between the spinneret and the first drivingrollers may be sufficiently low for the filaments to be disposed on thisroller without difliculty and stretched in the form of a tow rather thanassembled in compact form, so that all the filaments undergo exactly thesame extent of stretch.

On the other hand a regular stretch could not be effected if thefilaments were driven at the speed V before being cooled to atemperature not greater than T because under these conditions the fibreswould adhere to the driving rollers. On the other hands, if thefilaments were cooled to a temperature below T they would slip on therollers and it would no longer be possible to effect a regular stretch.

In the following examples, which illustrate the invention, the tenacityand the elongation are measured on the Instron dynamometer, thecontraction is measured on skeins after remaining in hot air at 150 C.for 30 minutes, the value of the modulus is given by the slope of thetangent to the origin of the dynamometric curve corresponding to aspecimen of a length of 50 cm. and to a break time of 20 to 30 secondsand the birefringence is measured on filaments without tension.

EXAMPLES 1-2 A polyhexamethylene adipamide having a relative viscosityof 36 measured at 25 C. on an 8.4% by weight solution in formic acid hasa transition point of the second order at 50 C. and its intialorientation temperature is C.

This polymer is extruded at 292 C. through a spinneret having 23 holesof a diameter of 0.34 mm.

The extruded filaments pass through a calm atmosphere maintained atambient temperature.

When these filaments have reached a temperature of 75 C., i.e. at adistance of 54 cm. from the spinneret, they are driven at 295 m./min. bya supply system consisting of 2 rollers heated at 75 C. and rotating inopposite directions, which are diagrammatically illustrated at 1 and 2in the accompanying FIG. 1.

The filaments thereafter pass through a zone 65 cm. long, in which acalm atmosphere at ambient temperature also obtains and in which theyare cooled to this temperature. They are then driven by a stretchingroller 3 associated with an idler 4 maintained at 25 C. Disposed in thepassage of the filaments between the stretching roller 3 and the idler 4is a batching device 5. The filaments are thereafter wound in knownmanner. The following results are obtained for 'various degrees ofstretch:

EXAMPLES 3-4 A polyamide identical to that of Example 1 is extrudedunder the same conditions with a rate of flow of 0.36 g./min. per hole,and then orientated under the conditions set out in the following table:

Example 3 4 Distance between spinneret and supply roller, cm 55 47Temperature of the filaments at the level of the supply rollers, C 55 65Temperature of the supply rollers, C 55 65 Peripheral velocity of thesupply rollers, m./nu'n 300 300 Distance between the supply andstretching rollers, cm 60 70 Peripheral velocity of the stretchingrollers, m./min 1, 260 1, 200 Temperature of the filaments at the levelof the supply rollers, C 25 25 Count:

dtmr 73 73 d- 66 70 Tenacity:

gJtex 43. 2 37. 8 g./d 4. 8 4. 2, Elongation, percent 35. 5 37. 6Modulus: g./d 30 27 g./tex 270* 248 Contraction, percent 5.9

These tests show that, in the temperature range between 55 and 65 C.,the temperature of the thread at the level of the supply rollers onlyslightly affects the strength and the elongation, which are above allinfluenced by the value of the extent of stretch.

On the other hand, if the filaments are cooled to a temperature of 45 C.before being passed over supply rollers at the same temperature, aregular stretch is no longer possible: slipping occurs on the supplyrollers and the degree of stretch cannot be maintained at a constantvalue.

If the temperature of the filaments at the supply rollers is above 100C., the filaments stick together and to the rollers: the stretchingcannot be eflFected under good conditions.

EXAMPLE 5-10 A polyhexamethylene adipamide identical to that of Example2 is extruded under the same conditions. When the filaments have reacheda temperature of 60 C., i.e. at 51 cm. from the spinneret, they aredriven at 300 m./ min. by supply rollers maintained at 60 C.

After having passed through a calm atmosphere over a distance of 60 cm.,maintained at ambient temperature, the filaments are driven bystretching rollers under the conditions indicated in the followingtable, in which the characteristics of the filaments obtained are alsoindicated:

Example 5 6 7 8 9 10 Speed of the Stretching rollers,

m. min 600 750 900 1, 050 1, 200

perature of the stretching 18. 9 27 29. 7 37. 8 46 g./d 1.5 2.1 3 3.34.2 5.1 Elongation, percent.-. 266 165 106 66 42 28. Contraction,percent. 1. 6 0. 6 1. 2 1. 9 3. 4 5. 5 Modulus of elasticity' g./tex 77.4 116 172 215 306 g./d 8. 6 12.9 19. 1 24 27. 6 Birefringence 0. 025 0.041 0. 048 0. 051 0. 053 0. 057

"It will be seen from these examples that it is possible to obtain bythe process of the invention polyamide filaments having high elongationand low contraction. Filaments stretched by conventional methods andhaving characteristics of tenacity and elongation substantiallyidentical to those of Examples 5 to 8 have substantially higher contractions of the order of 8l2%.

It is found that in the process of the invention the tenacity and theelongation of the filaments vary continuously as a function of theextent of stretch, while the values of the contraction pass through aminimum.

EXAMPLE 1 1 A copolyamide obtained from 95 parts by weight ofhexamethylene diamine adipate and 5% by weight of caprolactam, having arelative viscosity of 36, is extruded through a spinneret having 23holes of a diameter of 0.34 mm. at a rate of flow of 0.36 g./min./hole.At 55 cm. from the spinneret, when the filaments have reached atemperature of 55 0., they are driven at 300 m./min. by a system ofsupply rollers maintained at 55 C. After having travelled 60 cm. througha calm atmosphere maintained at ambient temperature, the filaments aredriven at 1380 m./min. by a system of stretching rollers at 25 C.

The filaments obtained have a count of 69 d./tex (62 d.), a tenacity of45 g./tex (5 g./d.), an elongation of 24.7% and a contraction of 8%.

EXAMPLES 12-13 Polyethylene terephthalate having an intrinsic viscosityof 0.67 has a transition point of the second order at a temperature T of70 C. and an initial orientation at a temperature T of 130 C.

This polymer is extruded at 285 C. through a spinneret having 30 holesof a diameter of 0.34 mm. in an atmosphere maintained at ambienttemperature.

At 53 cm. from the spinneret, the filaments have reached a temperatureof C. and are driven at 300 m./min. by a system of supply rollersmaintained at 90 C. After having travelled a distance of l m. through anatmosphere maintained at ambient temperature and having been passed overa batching device, the filaments, which have reached a temperature of 25C., are driven at 1500 m./ min. by a system of stretching rollers heatedat the temperature indicated in the following table, in which theproperties of the filaments obtained are also set out:

Example 12 13 Temperature of the stretching rollers, C 150 170 Count:

g./tex 41. 5 41. 5 g./d 4. 6 4. 6 Elongation, percent 20 19 Modulus:

g./tex 1, 080 950 g. d 104 Contraction, percent 12 9. 7

It will be seen from these examples that when the temperature of thestretching rollers increases, the tenacity and the elongation of thefilaments are only slightly modified, while the modulus and thecontraction decrease.

EXAMPLE l4 Filaments of polyethylene terephthalate which have reached atemperature of 25 C., and which have been extruded under the sameconditions as in Example 13 and are driven at 280 m./ min. by a systemof supply rollers maintained at 90 C., are passed over a first train ofstretching rollers maintained at 200 C. and rotating at a peripheralvelocity of 1400 m./min. The filaments are thereafter continuouslyconducted to a second train of stretching rollers maintained at 25 C.,which is situated at 30 cm. from the first stretching train and whichdrives these filaments at 1680 m./min.

The yarn obtained, of 150 d./tex d.), 30filaments, has a tenacity of60.3 g./tex (6.7 g./d.), an elongation of 9% and a contraction of 13.5%;its modulus is 1080 g./ tex (120 g./d.).

EXAMPLE 15 The polyhexamethylene adipamide filament of Example 10 isre-stretched to 1.4 times its length, at m./min., lfgopas sing it over acold finger and a plate heated at The resultant filament has a tenacityof 74 g./tex (8.2 g./d.), an elongation of 12.6%, a modulus of 414g./tex (46 g./d.) and a contraction of 4.7%.

This test shows that the process according to the invention makes itpossible to obtain polyamide filament of very high modulus and lowcontraction.

EXAMPLE 16 A polyethylene terephthalate identical to that employed inExample 12 is extruded and the filaments obtained are driven under theconditions described in the said Example 12. These filaments arethereafter passed over a system of stretching rollers maintained at 25C. and rotating at a peripheral velocity of 1500 m./min.

The filament obtained is re-stretched to 1.3 times its length, at 130m./min., by passing it over a finger maintained at 90 C. and a plateheated at 230 C. There is finally obtained a filament having a tenacityof 74 g./tex 8.27 g./d.), an elongation of 6.5% and a contraction ofWhat is claimed is: p V

1. A process for the production of oriented continuous filaments ofpolyesters or polyamides' of fiber-forming molecular weight by spinningthe polymer and orienting the resulting filament by stretching in whichthe'spinning and stretching are carried out as a single continuousprocess, which comprises as a series of successive steps, one followingimmediately on one another in the following order:

(a) extruding as continuous filaments the molten polymer into anatmosphere at substantially the ambient temperature; 1

(b) cooling the filaments so formed directly to a temperature T between55 and 130 C. which is (i) above 55 C., (ii) at least C. above thesecond order transition temperature of the polymer, and (iii) not higherthan the maximum temperature at which stretching fiaments of the polymerorients them;

(c) positively forwarding the filaments when they have reached the saidtemperature T at a speed V higher than the extrusion speed, whereby thefreshly extruded filaments are attenuated without being substantiallyoriented;

(d) cooling the filaments further to a temperature T below 75 C. whichis alsobetween T and the ambient temperature, by causing them tocontinue to travel through an atmosphere at the ambient temperature; and

(e) positively forwarding the filaments While they are at the saidtemperature T at a speed V which is greater than V the ratio V2/V1 beingfrom 3:1 to 6: 1, whereby the filaments so produced are oriented.

2. Process according to claim 1, wherein filaments of polyhexamethyleneadipamide are made, the temperature T is between 55 and 100 C., thetemperature T is between 55 C. and the ambient temperature, and thefilaments are forwarded in steps (c) and (e) by means of rotatingsurfaces whose temperatures are T and T respectively.

3. Process according to claim 1, wherein filaments of polyethyleneterephthalate are made, the temperature T is between and C., thetemperature T is between 75 C. and the ambient temperature, and thefilaments are forwarded in steps (c) and (e) by means of rotatingsurfaces whose temperatures are T and T respectively.

4. Process according to claim 2, wherein the temperature T is theambient temperature.

5. Process according to claim 3, wherein the temperature T is theambient temperature.

References Cited UNITED STATES PATENTS 3,400,192 9/1968 Hartmann et al.264-290 T 3,414,646 12/1968 Pitzl 264-290 T 3,448,186 6/1969 Nicita etal. 264-210 Z 3,452,131 6/1969 Geerdes et al. 264-210 Z 3,452,132 6/1969Pitzl 264-210Z 3,511,905 5/1970 Martin 264-210 Z 3,002,804 10/1961Kilran 260-210 F 3,199,281 8/1965 Maerov et a1 264-103 3,256,258 6/1966Herrman 260-937 3,361,859 1/1968 Cenzato 264-210 F 3,379,810 4/1968 Onoet al. 264-210-F 3,454,998 7/1969 Satterwhite 28-1 2,734,794 2/1956Calton 264-210 F 3,549,743 12/1970 Riordon 264-210 F JAY H. WOO, PrimaryExaminer US. Cl. X.R. 264-290

1. A PROCESS FOR THE PRODUCTION OF ORIENTED CONTINUOUS FILAMENTS OFPOLYESTTERS OR POLYAMIDES OF FIBER-FORMING MOLECULAR WEIGHT BY SPINNINGTHE POLYMER AND ORIENTING THE RESULTING FILAMENT BY STRETCHING IN WHICHTHE SPINNING AND STRETCHING ARE CARRIED OUT AS A SINGLE CONTINUOUSPROCESS, WHICH COMPRISES AS A SERIES OF SUCCESSIVE STEPS, ONE FOLLOWINGIMMEDIATELY ON ONE ANOTHER IN THE FOLLOWING ORDER: (A) EXTRUDING ASCONTINUOUS FILAMENTS THE MOLTEN POLYMER INTO AN ATMOSPHERE ATSUBSTANTIALLY THE AMBIENT TEMPERATURE; (B) COOLING THE FILAMENTS SOFORMED DIRECTLY TO A TEMPERATURE T1 BETWEEN 55* AND 130*C. WHICH IS (I)ABOVE 55*C., (II) AT LEAST 5*C. ABOVE THE SECOND ORDER TRANSITIONTEMPERATURE OF THE POLYMER, AND (III) NOT HIGHER THAN THE MAXIMUMTEMPERATURE AT WHICH STRETCHING FILAMENTS OF THE POLYMER ORIENTS THEM;(C) POSITIVELY FORWARDING THE FILAMENTS WHEN THEY HAVE REACHED THE SAIDTEMPERATURE T1 AT A SPEED V1 HIGHER THAN THE EXTTRUSION SPEED, WHEREBYTHE FRESHLY EXTRUDED FILAMENTS ARE ATTENUATED WITHOUT BEINGSUBSTANTIALLY ORIENTED;